Force PDFs in Lightbox

Hi, I've been using Bumpbox to display PDF files on my website in a popup lightbox format. I've been using it for over a year and never had any problems, but just recently it stopped working. An empty lightbox would pop up and the PDF would be downloaded straight to my hard drive.

I use Firefox and have it set to automatically download most files, including PDFs. However, I don't believe this was a problem before. Since Bumpbox was being used, it would display PDFs in the popup and only downloaded them from direct links on other sites. I changed my PDF settings to "preview in Firefox" and now it's loading in the lightbox just fine. I don't know if it's a result of having updated to the latest version of FF or what, considering I didn't personally change anything since it was last working.

My concern is that whether or not it displays properly (instead of downloading and leaving users with an empty box on the screen) now seems to be user-dependent. Is there a way to use Javascript or PHP or anything to force PDF files to open in the lightbox (effectively overriding browser settings)? Because it's going to look really unprofessional if I have multiple pages that are supposed to be read on my site and people browsing through it simply end up with an empty lightbox on the screen.

I recently started redoing the site with Joomla so I don't know if that's causing the problem, although I moved the earlier version (raw CSS/HTML) into a subdirectory, where the overall site functions as it always did, and the same issue is happening there too. So I'm just wondering if it might be an issue with newer browser versions.

Is there a way to use Javascript or PHP or anything to force PDF files to open in the lightbox (effectively overriding browser settings)?

No.

Looking at the Bumpbox demo, it's just putting the PDF file into an iframe. The browser is going to do whatever it is set to do when you visit a PDF file (display it inline, download it automatically, prompt you to download it, etc.). There is no way to override that behavior.

Thanks, I ended up just using the Bumpbox but including a note that if the lightbox pops up empty, the PDF was likely downloaded per their browser settings. Best compromise for now, I think. Appreciate the help!